Anesthesia and Liver Disease E.A. Steele, MD May 4, 2005

Liver Anatomy

Liver Anatomy cont.

Liver Blood Flow Portal Vein 70% of total flow 50% of oxygen (only has 85% sat) Dependent upon flow thru GI tract Hepatic Artery 30% of total flow 50% of oxygen autoregulated to meet liver demand

Metabolic functions Carbohydrate metabolism – glycogen storage Fat metabolism – fatty acids Protein metabolism – protein deamination to urea, amino acid conversions, plasma protein production Drug metabolism Other - T4 to T3, vitamin storage

Protein Metabolism Deamination – converts a.a. into carbohydrates/fats with ammonia as by- product. Ammonia is toxic 2(Ammonia) + CO2 = urea Plasma proteins –Albumin, coagulation factors (exc. Factor 8 and vWF), plasma cholinesterases, transport proteins

Bile Bile ducts become R & L Hepatic Ducts become hepatic duct, joined by the cystic duct to form the common bile duct to the sphincter of oddi along with the pancreatic duct Bile acids for cholesterol elimination and fat absorption (fat soluble vitamins) Bilirubin exrection –heme – RES – Bilirubin in blood (unconjugated) – liver (conjugated) – excreted in bile mostly, small amt abs in blood or converted in intestines to urobilinogen

Evaluation of liver function Large functional reserve of liver, hence there may be significant liver damage before abn. Laboratory tests. AST/ALT Bilirubin Alk Phos Albumin Ammonia Coags

Aminotransferases Aspartate aminotransferase (AST=SGOT) Alanine aminotransferase (ALT=SGPT) Alpocanine aminotransferase (APT=SPOT) Released from liver cells as they die Normal levels below 40ish. Alcohol ALT<AST

Bilirubin Unconjugated –Hemolysis, congenital defects of conjugation Conjugated –Hepatocellular dysfunction, obstruction –kernicterus Total

Albumin Low levels –Decreased production Liver disease, malnutrition, stress –Increased loss Renal, gut

Coagulation Protime/INR –Fibrinogen, Factors V, VII and X, prothrombin –Factor VII has a half-life of 5h, with acute liver injury can see prolongation of PT quickly –What’s the point of giving FFP the night before surgery? Very little. –FFP given just before surgery –Vitamin K 12-24h before surgery

Effect of Anesthesia on the Liver Hepatic blood flow –Decreased portal vein flow –Decreased hepatic artery flow (decrease C.O., Decreased MAP) –Ventilation (PPV, PEEP) –Surgical procedure

Anesthetic effects (cont) Biliary function –Sphincter of Oddi spasm Glucagon Halothane hepatitis Degree of metabolism Pt. at risk: Female, fat, forty, repeat exposure

Post-op jaundice Most likely due to pre-operative dysfunction Drugs (incl OTC and herbals), sepsis, exogenous bilirubin load (old blood), occult hematomas, hemolysis, perioperative events (hypotension, hypoxia), co-morbidities (CHF), Remote possibilities: “Benign postoperative intrahepatic cholestasis” assoc. with long surgery complicated by hypotension, hypoxemia, massive transfusion; immune-mediated hepatoxicity

Cirrhosis Affects all organ systems Surgical risk related to degree of hepatic impairment all other things being equal (emergency surgery, type of surgery, comorbidities)

Child-Pugh (or Child-Turcotte)score Assigns points (1, 2 or 3) for stigmata of cirrhosis Ascites, bilirubin, albumin, PT/INR, Encephalopathy Basically, the healthier you are the lower the score. A low score is Grade A – well compensated disease with a 1-2 year patient survival of %. Grade C, decompensated disease, 1-2 year survival at 35-45%. This corresponds to perioperative mortality rates of 10, 31 and 76% for increasing Grades. MELD scores are prob. Similar to Child-Pugh in predicting mortality. Model for end stage liver disease score.

Surgical/Invasive Procedures ERCP TIPPS Cholecystecomy Hepatic resection Liver transplant